There is a constant danger in underground mining of the collapse of the mine tunnel. Many different arrangements have been proposed to inhibit the collapse of, in particular, the roof of a mine. Support installations for supporting the side walls or roof of an underground mine are often categorized as primary support installations and secondary support installations. Primary support installations are those utilized during the initial excavation of the mine and may, for example, involve the installation of rock bolts into the roof and walls of the mine to stabilize the strata. Secondary support installations are used to provide stability to the strata during and after the mining operations. Examples of secondary support installations include the use of roof bolts, cable bolts or support structures erected within the mine, such structures including beams and support columns, which provide additional structural support to the side walls and roof of the mine tunnel or shaft. For example, structures of this type may comprise timber or steel props or cribs, cast concrete columns and cribs or varied combinations of these materials plied together. Other structures in the art are constructed in-situ and are pumped, poured or cast with varying cementitious or other material to establish a secondary support installation. Such constructions, however, have certain drawbacks. For example, supports constructed of precast concrete and cementitious material require form work to be set, mixing and hatching systems established and managed and employment of a number of operators underground on site during construction. Furthermore, such installations can only function following the separation of strata and the convergence of the roof or when the heave of floor has begun before they begin to function in the designed manner.
Another type of support that has found considerable success is the type that comprises an outer shell, which is filled with a compressible or crushable material. The outer shell is also designed to collapse or yield at least to a certain extent as a result of, for example, subsidence of the main roof. The problems associated with supports of this type are that they are time consuming to install. Furthermore, it only provides a passive support arrangement in that it needs a subsidence to occur before it will commence to load the mine roof.